Aircraft



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original Filed Feb. r2', 1954 e shams-sheet 1 Dec. 9, 1941.v H. H.PLATT 2,265,193

AIRCRAFT origin@ Filed Feb. 2, 1954 a sheets-sheet@ INVENTOR. 72me ZmzcZHPla- 'De.--9,1941.' 11H. PLA" 2,265,193

Incumoriginanv Filed Feb. 2, 1934 s sheets-sheet s 47 so P 5 JV 49 /50 47 INVENTOR. zm'maphz Dec' 9 1941.

H. H. PLATT AIRCRAFT original Filed Feb. 2, 1954 8 Sheets sheet 4 Lul H. H. PLATT AIRCRAFT Original Filed Feb. 2, 1934 8 Sheets-Sheet 5 FJO RNEYS.

9, 1941. 4 H. H. PLATT 2,265,193

AIRCRAFT original Filed Feb. 2, 1934 8 sheets-sheet e y gf 46 INVENToR. fvna/HPh Dec. 9, 1941. H. H. PLA-r1 2,265,193

AIRCRAFT 4I`.'LE,J`J'IB.1 Filed Feb. 2, 1934 8 Sheets-Sheet 7 INVENTOR. Lvc'nJ H. H. PLATT Dec. 9; 1941.

AIRCRAFT Original Filed Feb. 2, 1934 8 Sheets-Sheet 8 s INVENTOR. Haw'zamz /71/ Pa# BY Y v C j Armlevs.

Patented Dec. 9, 1941 UNITED STATES- PATENT OFFICE amcaarr Haviland' n. rim, New vork, N. Y., maar zo Rota Researc Corporation, Philadelphia,

Pa., a corporation of Pennsylvania Original application February 2, 1934. Serial No.

Divided and this application March 22, 1937, Serial No. 133,072

32 Claims.

i ing practical utility. l

It is well known that the helicopter has hitherto been prevented from achieving the advantages of controlled vertical as well ashorizontal flight because of certain limitations, to wit:

Diiiiculty in balancing the torque `reaction of the lift screw; instability in various flight condil tions; inadequacy of control; insufficient provision for eiilcient propulsion in forward flight; insuiiicient provision for safe landing in case of vengine failure; excessive resistance to forward motion; mechanical complexity, particularly in the power transmission; excessive weight of sup-l porting and power transmission means: andv danger from gyroscopic effects.

One of the objects of my present invention is to overcome in a practical way, some of the above outlined limitations of the prior art.

With such, and other objects in view, which will appear more fully from the following detailed description', my invention includes novel arrangement of anti-torque, surfaces or aerofoils cooperating with the slip stream of the lift screw to counteract the torque reaction incident to the transmission of power from the body of the craft tothe lift screw, which anti-torque surfaces or aerofoils will not only correctly balance the torque reaction but will offer low air resistance in forward flight.

Another phase of my invention contemplates or includes novel control means cooperating with the anti-torque surfaces for controlling the forward motion, or the direction of pointing of the aircraft, which will be effective not only in forward flight, but which will also be effective in vertical ascent or descent, and also when the aircraft has no air speed in any direction. My invention further contemplates means whereby the proper function of these controls may be attained in power-off flight conditions.

VAnother phase of my invention contemplates the 'use of a lift screw, an articulated rotor with the blades so pivoted or articulated and with the pivotally related portions or members so interconnected that the blades will automatically assume positions in which all the forces, including the centrifugal forces acting upon the blades, are in complete balance, whereby undesirable gyroscopic eects are largely eliminated, and great .stability provided at low speeds, particularly in vertical operation, by reason of the dihedral angle presented by the rotor while in operation.

A further phase of my present -invention contemplates or includes automatic means for vary- -ing the pitch of the blades of the rotor which will be responsive to the driving torque, thus automatically varying the thrust and the rotative resistance of the rotor according to .the requirements of the various conditions of engine throttle.

' without the need of separate manual control on the part of the operator.

Another phase of my invention contemplates and includes over-running clutch means associated with the rotor, in combination with said automatic torque-responsive pitch control, which automatically insures the correct blade angle setting for safe descent in case of power failure, and which thereby greatly increases the factor of safety of the craft by guarding against sudden l, and unexpected engine failures, and-by making 'the craft proof against any error in judgmentor carelessness on the part of the operator, since the craft is automatically adjusted for vertical descent in the event of a power failure.

Another phase of my invention includes means 'including control surfaces responsive to the rotor slip stream whereby both vertical and horizontal flight may be effected by a change. of attitude or by a variationof the angle or "tilting of the fuselage in the vertical median plane, so that a 'horizontal component of the thrust of the rotor may be developed, variable at the will of the operator, according to the extent of the tilting of the fuselage. Thus, this phase of my invention contemplates rotor-slip-stream responsive means for tilting the craft in the vertical median plane,

between suitable limits, for developing a horizontal component of the thrust of the rotor for the desired horizontal or forward propulsion. By

" reason of the articulated character of the rotor,

and its automatic adjustment to the forces imposed upon it, one phase of my present invention provides more emcient forward propulsion by the elimination of power losses generally avoidable in conventional form of propulsion by means of conventional propeller arrangements.`

Another phase of my present invention consists of acertain offset arrangement of the antitorque surfaces, whereby certain undesirable distribution of forward night forces. now common to articulated rotors, maybe satisfactorily overcome.

Another phase of my present invention consists of certain novel arrangement of engine controlling means including the provision of radiators in the anti-torque surfaces, whereby the engine may effectively be cooled under all power-driven conditions.

Another phase of my present invention consists of the novel combination with some of the foregoing, of adjustable under-carriage for permitting the inclination of the craft to the desired angle, while the craft is on the ground, so that the relation between the horizontal and vertical components of the thrust of the rotor may be controlled even when the craft is on the ground, thereby facilitating ground maneuvers and facilitating take-offs and also landings.

Another phase of my present invention consists of the novel combination with a rotor, of a "geared engine having a generally upright shaft or crank-shaft, with the engine more or less directly adjacent to' the rotor, with the rotor mounted upon the extending shaft in a more or less closely coupled relation, without the use of any intermediate shafting, and whereby also the rotor may be supported directly by the housing of the geared engine.

Another and alternative phase of my present invention consists of certain novel means for longitudinal control, including means for tilting the rotor, the power plant, and the anti-torque surface assembly relative to the fuselage in the vertical median plane of the latter.

My invention also includes other novel features of construction forming part of one or more of the principal phases of the invention above outlined, all of which will appear more fully from the following detailed description.

For the purpose of illustrating my invention, I have shown in the accompanying drawings, forms thereof which are at present preferred by me, since the same have been found in practice to give satisfactory and reliable results, although it is to be understood that the various instrumentalities of which my invention consists can be variously arranged and organized and that my invention is not limited to the precise arrangement and `organization of the instrumentalities as herein shown and described.

Referring to the drawings in which like reference characters indicate like parts: A

Figure l represents a generallyv schematic top plan view of an aircraft embodying my invention, this top plan view showing the general arrangement and the disposition of the rotor, the fuselage,l the anti-torque surfaces, and the tail surfaces in relation to each other.

Figure 2 represents 'a similar and also more or less schematic side elevational view of the same, illustrating the general arrangement and disposition of the anti-torque surfaces and .the lateral control means connected therewith.

Figure 3 represents a front elevational view of the same, also shown in more or less schematic fashion, further illustrating the relationship of the various parts, -particularly the setting of the anti-torque surfaces; the tail surfaces, and the under-carriage.

Figure 4 represents a diagrammatic top plan view of the lateral control elements (the supporting structure, such as fuselage, being omitted), shown on a scale somewhat different than the scale to which Figure 1, for instance, is drawn. f

Figure 5 represents a corresponding diagrammatic front elevational view of the front antitorque surfaces and control flaps associated therewith, and forming a part thereof, further illustrating the operation of the lateral control means.

Figure 6 representsA a fragmentary sectional view, on an enlarged scale, of the rotor hub and one of the pivotal blade supports, including the pitch regulator.

Figure 7 is a fragmentary sectional view on av similarly enlarged scale, generally on line 1-1 of Figure 1, showing the rotor hub, the blade attachment,` the pitch regulator and a more or less diagrammatic outline of a power plant and transmission arrangement in close coupled relationship to the rotor.

Figure 8 represents a diagrammatic plan view of the parts shown in Figure 6, arranged to illustrate the operation of the pitch regulator and showing also the relationship of some of the forces acting upon the rotor blade, the balanceof which determines the pitch.

Figure 9 represents. a diagrammatic side elevational view of the aircraft embodying my in- `vention, shown generally in a condition of flight and arranged to illustrate a phase of the operation of the longitudinal controls.

Figure l0 represents a similar diagrammatic side elevational view of the craft embodying my invention, illustrating a different phase of operation, that is, through a different setting of the longitudinal controls.

Figure 11 represents a diagrammatic front elevational view of any craft (not embodying my invention) illustrating a state of lateral force unbalance existing in the forward night of an aircraft supported by a single articulated rotor.

Figure 12 represents a diagrammatic top plan view of one form or one arrangement of the antl-torque surfaces according to my invention,

illustrating the means of neutralizing the side force resulting from the condition shown in Figure 11.

Figure 13 represents a diagrammatic' front elevational view, similar to that shown in Figure 11, but illustrating the complete force balance obtainable by the meansY of my invention illustrated in Figure 12.

Figure 14 represents a diagrammatic side elevational view illustrating a method of varying 'the emcacy or effectiveness of the lateral con- .trols in forward flight as well' as reducing the drag of the fuselage and anti-torque surfaces.

Figure 15 represents a diagrammatic side elevational view of a modified form of aircraft embodying certain alternative phases or features of my present invention, and differing from the construction illustrated inI Figures 1, 2, 3, 4, 9, 10, 12, 13 and 14, principally in the means provided for longitudinal control.

In the accompanying drawings, the fuselage of the aircraft of my present invention is designated generally by the numeral i6. The fuselage may be of any suitable shape and construction, as may be necessary to provide seating space for the pilot and passengers, door and window space, attachment for the landing gear and anti-torque surfaces, suitable mounting for the power plant, and as otherwise may be required by the necessary strength and wind resistance.

The lift screw or rotor, designated generally by the numeral l1, is lmounted above the fuselage and is arranged to rotate about a generally upright axis passing through the central portion of the fuselage.

'I'he rotor comprises a plurality of aerofoil blades I8 of suitable cross-section. Three blades are shown in the illustrations although it is possible to vary this number, 'and for some purposes it may be desirable to use four or more blades. Each of the blades I8, as shown particularly in Figures 6 and '7. is attached to the driving hub I 9 through an intermediate link or stub 20, which may be of tubular formation or of any other suitable cross-section.- The stubs may be enlarged at each of their ends, to form the outer members of pivot joints. The inner end of each stub is pivotally attached to one of a plurality of suitable lugs 2I yby means of a pivot pin 22, which passes through a hole in the lug and through suitable bearing openings in bosses formed in the enlarged inner end of the stub 20 which surrounds the lug 2I. The pin 22 may be held in place by anysuitable-means, as for instance, by the nat-head pin 24 and a cotter pin extended through `the free end thereof. l

The pivot jointsso formed, allow the stubs 20, and their respective blades I8 to swing or flap freely in corresponding planes in which the hub axis generally lies; the downward limits of deflection being fixed by any suitable means known inthe art or by the contacting of the stub end with the hub, as at 25, while the upper limits of deflection may be similarly determined by the contacting of the upper terminal edge (2S-a) of the stub 20 with the hub. These limits are established arbitrarily by the form of the stub-end,

and are so arranged as not to interfere with the perfect freedom of the blade (within the necessary limits of downward and upward deflection) to find its equilibrium position, as determined by the balance of centrifugal and lift forces, under all operating conditions. l

At its outer end, the stub 20 is attached to the tubular spar 26 of the blade I8, by means of a double pivot joint including the pivot pins or trunnions 21, which may be secured tothe stub 20, by threading into bosses formed in its enlarged outer end (or by any other suitable means) The axis of the trunnions 21 is disposed generally transversely of. the direction of the axis of the pivot pin 22, and more or less at a right angle thereto. As a result, the blade is permitted to swing freely, within suitable limits, in the surface of rotation, and is permitted under all operating conditions, to assume a position of lag determined by the balance between the cen.-

trifugal force of the blade and the aerodynamic drag force on the blade. The pivot pins or trunnions 21, instead of engaging the blade spar 26 directly, are journalled in, and engage appropriate opposed bearing openings in an annular collar or fitting 28, which is recessed to receive any suitable thrust bearing, such as the ball thrust bearing 29. A sleeve 30, surrounding andv rigidly attached to the inner end of the blade spar 26 (by welding or otherwise) is longitudinally retained, with rotational freedom, within the annular fitting 28, by any suitable means, such as the nut 3| and the washer32. The outward force of the blade, resulting mainly from the centrifugal force due to its mass, is thus borne by the ball (or other) thrust bearing and the end of the sleeve III, in coaxial relation thereto, and meshes with a corresponding bevel-gear segment 34 rigidly attached to, or formed integrally with. the end of the stub 20, in coaxial relation to the pivots or trunnions 21. It is evident that a lag of the blade under the influence, for example, of an aerodynamic drag force, will cause the bevel-gearsegment 33 to roll on bevel-gear segment 34, thus causing the blade spar sleeve 39, spar 26 and blade I8 to rotate on their common axis. and so to change the pitch of the blade, that is, its angle relative to the surface of rotation. 'I'he two bevel-gear segments may be replaced by a pin and slot or other suitable linkage, for effecting the mechanical correlation of the lag and pitch angles of the blade, which constitutes one phase or feature of my invention.

The angular deflection of the blade I8 with respect to the stub 20 (about the pivots 21) is preferably limited by any suitable means, as for instance, but causing the opposed terminal portions of the edge of the segment 33 to abut against corresponding end portions of the stub 28. 'Ihe opposed terminal portions of the segment 33 are ypreferably blank, that is, devoid of teeth, soas to form better stops The forward stop is preferably so set as to limit the forward deflection of the blade to approximately the angular position (about the pivot 21) normally assumed by the blade under purely autorotative conditions (or slightly ahead of such position); while the rearward deflection is preferably set to correspond to the maximum bladepitch angle which may be desired or permissible under maximum power-loading of rotor. v

The rotor hub I9 is preferably rigidly mounted on the short drive shaft 36, by any suitable means, such as the splined construction shown, the nut 31 and washer 38. The drive shaft 36, suitably journalled in the crank case supporting structure or housing 39 of the geared power plant 40, is

' driven by the crank shaft 4 I through the reduction gearing 42; 42-a; 42-b, and 42-c, housed in the housing 39. 4The cylindrical casing 43, interposed between the crank shaft and the reduction and mechanism for actuating it, in order to stop blade is free to rotate on the axis of the spar 26,

with a minimum of friction, while 'at the same time freely pivoted aboutthepivots 22 and 21.

' A fragmentary bevel-gear, or bevel segment 33 is secured to, or formed integrally with the outer the rotation of the rotor after landing. If desired, the free-wheeling or over-running clutch may be placed on the delivery end of the gear train, as for instance in the hub of the last gear (adjacent to rotor shaft) or in a suitable housing intermediate the last gear and the rotor shaft.

The power plant 4l) is rigidly supported on suitable horizontal frame members 44 and upright frame members 44-a of the fuselage, as by means of the fittings 45. While the power plant shown is of the radial l-iquid-cooled type, the advantages of this novel arrangement of closecoupled rotor and power plant mounting (which are, among other things, rigidity; reliability; simplicity; and light, weight) are not confined to any one form of engine.

The frame of the fuselage is extended at each Vend to support the plurality of antitorque surfaces 46 which are cambered airfoil surfaces set with their leading edges generally upward, but so disposed as to meet the rotor slipstream, or air A forced downward by the rotor when power driven,

at a lift angle. Furthermore, all the antitorque surfaces are so inclined with relation to the rotor slip stream as to produce lift forces tending to rotate the fuselage in thesame direction and about the same axis as the rotor, which is in the direction opposite to the torque reaction incident to the power delivered into 4the rotor.

With sufficient area and suitable proportions, the antitorque surfaces are capable-of providing a complete force balance, thus enabling the aircraft to hover motionless in the air or rise vertically without any tendency to turn or sideslip. This completeness of balance is not possible withany unsymmetrical arrangement of antitorque moments. Furthermore, the` parallel arrangement of the antitorque surfaces, with the minimum of area opposed toforward motion, permits the attainment of the highest possible ight speeds, because the drag ,of the anti-torque elements is at a minimum in forward night. While four antitorque surfaces are shown as being probably most suitable for the design illustrated, any other number, such as two or six may alternatively be used with modified forms of the design.`

For purposes of diirectional control and of regulation of the magnitude of the anti-torque moments, to meet varying conditions of operation, each one of the anti-torque surfaces is fitted at its lower, or trailing, edge with a hinged i flap l1, similar to the aileron of the conventional airplane wing. These flaps connected by the link rods 48-e and -L which are in turn attached to control cables 49 running over'pulleys 50 fixed to the frame, as particularly illustrated in the diagrammatic Figures 4 and 5. The control cables (shown broken in Figure 4 in order to bring the parts close together) are led into the fuselage and are attached through two cross strands to the horns or bell-crank arms 5i and 52 of the two coaxially mounted rudder bars 53 and 54, respectively, which may be conveniently located with relation to the pilots seat 55. With the arrangement shown, pushing forward with the right foot on rudder bar 53 will move all four control flaps in such a direction as to increase the effective camber of each of the four antitorque surfaces, while a similar forward motion of the left foot acts correspondingly to decrease their effective camber. On the other hand, pushing forward with the right foot on the rudder bar 54 until itis moved into a transverse position swings the flaps into the dotted positions 56, at which the camber and angle of the antitorque surfaces are approximately neutralized for autorotative conditions of operation. The motion of the aps resulting from turning the' rudder bar` 54, is now opposite in direction to that produced by the turning of rudder bar 53, which has been swung to an oblique position by the act of turning rud der bar 5l into the transverse attitude.

Attached to the rear end of the fuselage frame extension is the tail assembly consisting of a transversely pivoted control surface, or elevator 51, which is connected in the manner usual in airplane practice to a control stick of conventional design (not shown). At each end of the elevator is mounted a pivoted aileronl58. set at a dihedral angle suitable for providing adequate stability in forward flight. I'he ailerons are also connected to the control. stick in the manner usual in airplane practice for opposite or differential movements. A fixed vertical iin 59 -is 4provided fordirectional stability, although its function may alternatively be served by an extension of the rear anti-torque surfaces. The

elevator 51 differs from that usual in airplane practice in that it has no horizontal xed iin associated with it, and in that it is equipped with two forward extensions, or tabs 60, capable of ben the two front wheels 8l being attached to the' fuselage by suitable shock absorbing struts 62. The third wheel 64 is mounted at the rear of the fuselage by means of an adjustable strut 63 which may be raised or lowered at the will of the pilot y by suitable mechanism within the fuselage, such as a thread and nut actuatedby a worm wheel and worm, or the like (not shown). The rear wheel may thereby be raised or lowered so as to change the inclination of the craft while resting `on the ground. If desired, any or all of the wheels may be equipped with brakes and stops to prevent swlveling, at the will of the operator, for aid in ground maneuvering. Moreover, any or all of the three caster wheels may be replaced by plain wheels, skids, floats, skis, etc., as may be required for different 'types of service. Also the number of ground contacting members may be varied from the number shown.

In the arrangement illustrated in Figure 15 longitudinal control is obtained by tilting the rotor relative to the fuselage instead of by tilting the entire machine. Since the simplicity of the rotor drive would be impaired by an articulation ofthe drive shaft and also because a shift in rotation axis relative to the antitorque surfaces would give rise to an unbalanced torque reaction component, the rotor. I1, the power plant (here shown covered by a stream-line fairing 65) and the antitorque surfaces I6 are maintained in rigid alignment in the same relationship as before. The anti-torque surfaces are in this case however, not supported by the fuselage frame but,

through suitable framework 6B, are attached dibut as close to the hub of the rotor blades as possible structurally, thereby to reduce and minimize the moment produced by the rotor thrust, about pivot 10, and thereby to minimize the manual effort which may be required for operating the tilting control. The angular relation of the fuselage to said assembly may be varied, and means are provided whereby the pilot may change this angular relationship at will. The control means provided for this purpose may be any of a number of simple mechanical arrangements of which the one employed here has been chosen primarily .for cleanness in illustration. It consists in a sprocket 69 rigidly attached to the power plant, or other suitable part of the aforementioned assembly, coaxially with respect to the pivot 10, a second sprocket 1l, the control stick 14 of conventional design pivoted in the usual manner at 15, and a link 18 connecting the lower forward to the position shown, and mounted directly on the fuselage 61, their control connections to the control stick I4 remaining of the type hereinabove described.y I

The directional control provision is th'e same as in the rigid fuselage construction hereinabove described, except that additional means (not shown) are employed for assuring proper opera,

tion of the actuating cables regardless of .the angular relation between the fuselage and antitorque surfaces. Since devices for this purpose are well known in the mechanical arts, no specific description is included here. Thus, for instance, the cables 49 may be extended upwardly to the rotor-motor assembly and then outwardly to the ailerons 41 (over suitable pulleys), or the transmission of the motion from th'e fusel e to the overhead rotor, motor, and antitorque assembly may be'eil'ected through shafts and suitable gearing, or by other suitable mechanical means. In either event, the transmitting meanswould enter e rotor, motor and antitorque assembly through me means more or less concentrically related or coaxially related to the pivot 10.

'Ihe landing gear is similar to that previously described, except that the provision for changing the ground attitude is omitted because the rotor tilting control serve s thesame purpose.

AIn Figure the dot-dash lines' 18 show the approximate outline of the conical surface 1n which th blades I8 revolve when supporting the weight of the machine in vertical flight.

In aircraft, which at times movel through the air slowly, diiculty has been experienced in cooling the engine adequately, owing to 'the low air velocities available. In a machine designed to stand still in the air this problem becomes even more acute. According tQ-one phase of my present invention, the antitoiuue surfaces 46 may be used as radiators by .circulating the cooling liquid 50 from the engine cylinder jackets through tubes embedded in, or forming the skin of the fixed portions ofall or a the antitorque surfaces or elements. The `ititorque surface supporting frame members may, if of tubular construction, be employed to convey the liquid to and from the radiating surfaces; and a method of connection to the engine cylinders is illustrated at 19 in Figure 7, wherein the tubular frame members 44 and M-a serve as conduits, through the fittings I9 which. also serve to secure the engine to the horizontal frame members. With this arrangement, the air velocity of the rotor slip stream is always available when the power is on and the additional air resistance of a radiator or of cool ing fins is avoided. Likewise, in forward speed, th'e air-speed of the craft is not greatly hindered since the antitorque surfaces or elements present relatively small areas in the forward direction.

One of the greatest difficulties heretofore encountered in helicopter design has been to provide both for adequate lift eiiiciency and means for slow descent without power. While each condition can easily be met separately, the required in the two cases. If the lift screw is designed to rotate solely under the influence of the aerodynamic forces imposed upon it by the relative air-flow resulting from the motion of the machin 5 through the air. which as is well known. is capable of providing safe descent without power. the pitch of the blades must be made relatively very small. On the other hand, for eilicient vertical lift under power, a relatively much larger pitch angle is required. Pitch control mechanisms operated by the pilot I have deemed undesirable because, among other things, such pitch-control requires the unfailing judgment on the part of the pilot for correct operation. These dimculties are fully met in my novel construction by the simple automatic pitch regulator.

The operation of this device is illustrated by the vector diagram, in plan view, in Figure 8, which shows (schematically) one blade I8 and its connections to the driving hub I9, the proportions being somewhat altered from those of Figure 1 for the purpose of greater clarity. The arrow 80 indicates the direction of rotation of the blade about the hub axis. The arrow 8| represents the direction and magnitude of the centrifugal force acting radially outward from the center of gravity of the blade. The arrow 82 represents the tangential force resulting from the air resistance or drag of the blade, and the arrow 83 represents the resultant force acting on theblade from the combined effects of the centrifugal and drag forces.-

Obviously, if the blade is freev to swing about the pivot 2l, it will necessarily be in equilibrium only when the line of the resultant force 83 '35 passes through the pivot 2l. Therefore, if the drag force 82 is changed, the direction of the force 83 being thereby also changed, the blade A must swing about the pivot 21 until the resultant force line is again brought into the pivot axis. The drag force 82 must at all times, during steady running, be balanced by the driving torque applied at the hub; for otherwise the unbalanced drag would cause a change in blade speed. There'- fore it is seen that the angle of lag of the blade ls with relation to the stub zn, 1s at au times,

during steady running, a function only of the driving torque. For example. when there is no driving torque, as in autorotation, there is no lag and the stub 'and blade are in line. On the other hand, whenever the engine throttle is wide open the'blade lags behind the stub to a maximum angular extent, determined by the weight of the blade and the relative proportions of the parts.

As has already been shown, any lag of the blade is accompanied by a rotation of the blade on its axis as the result of the geared connection between the stub and the blade, as illustrated particularly in Figure 7. Furthermore, it will be noticed from consideration of Figure 7 that an increase in lag is accompanied by an increase in pitch and vice versa. Consequently it is evident that an increase in driving torque is automatically accompanied by an increase in pitch.

Now if the gear ratio of the pitch regulator is suitably proportioned the blade may be given the best autorotative pitch setting when there is no driving torque and the most elilcient lifting pitch when the full power is applied. Furthermore,

the change in pitch will take place between the two extremes so as to maintain the'rotational velocity of the blades approximately constant, or

to increase or decrease it with increasing torque,

according to the gear ratio employed. This charsettings of the lift screw pitch are very different acteristic of the automatic pitch regulator phase of my invention is especially valuable when the 4internal combustion engine is used as a source -of In the hereinabove described phase of my in- 5 vention. the blade angle may be increased (upon the application of power) or decreased (as required for auto-rotation) gradually in proportion to the torque. Thus, instead o f connecting power may be delivered to a separate concentric shaft either surrounding the shaft 35 or extending through said shaft (in which case the shaft 36 will be tubular) and the torque transmitted from one shaft to the other through spring members which would be deformed in proportion to'theftorque delivered so that there will be a difieren-t angular disposition of the two shafts with respect to each other, according to the amount of torque being delivered from one to the other. This angular displacement of the driving shaft with respect to the driven shaft (according to the amount of torque being delivered) may then be transmitted to blade angle control means similar to the members 33 and 34, 25

so that as the springs are deformed more and more by the increase in torque (that is, power delivered) the blade angle or blade pitch will be smoothly and automatically increased so as to provide a greater blade angle for the various conditions of vertical operation with powerdriven rotor and so that when the power is removed from 'the rotor the blade angle will Asmoothly and automatically shift back into the so disposed as to derive a lift force from the airow over them, which tends to rotate the structure to which they are attached in the same direction as that of the rotor rotation; that is, opposite to that of the torque reaction.

In the novel arrangement of antitorque surfaces which I have disclosed the antitorque moments so developed are symmetrically disposed about the rotation axis. the power directly to the rotor shaft 36, the lo With dierent operating conditions the torque reaction, as well as the air velocity over the antitorque surfaces, varies. To insure a correct balance at all times means are provided for varying the antitorque moment. The novel means here disclosed for this purpose 'include the mounting of a hinged ap 41 at the lower or trailing edge of each (or some) antitorque surface or element. The deiiection of these flaps on their hinges, by the actuation of appropriate controls, as illustrated particularly in Figures 4 and 5, varies both the effective camber and the eective angular setting of the surfaces` and thus changes the antitorque forces produced. I may pivot the entire surfaces, or I may apply the control means to less than the whole number of antitorque elements or surfaces, or separate auzdliary surfaces lmay be employed.

Thus, as the machine rises, if it tends to turn to the right, for example, the pilot sitting in seat A55, or seat 16, (Figures 4 or15) presses forward with his left foot on the rudder bar 53, thus de-r iiecting the aps 41 in the direction of reduced camber and angle. The antitorque forces are thereby reduced and the torque reaction unbal- -auto-rqtative' condition. that is. t0 the lesser 35 Varmed sufficiently to rotate the craft to the left.

angle.

In this manner, the transition from the autorotative ight to power-driven rotor night, and vice versa, may be effected more smoothly and with less effort and skill Yon the part of the operator.

By this means also, the transmission of power from 'engine to rotor may be more effectively 'cushioned by the spring member through which the power'is actually transmitted from the driv- 45 -ing shaft to the, driven shaft of the rotor.

In' 'such automatic night control of the rotor blades, the stubs 20 are eliminated and the blade angle control' means similar to the members 33 close proximity to the concentric shafts.

' The following is a consideration of the lght operation and control of lthe aircraft of my present invention. In order to take on vertically from the ground itis only necessary to start the 'or concer-non the part of the pilot. When the w ,rotor'gets up to speed the machine willimmediately leave the grolmd and rise vertically or in whatever inclined path is determined by the control settings.

the machine leaves the ground the reaction from the torque of the rotor will tend to spin the entire structure of the craft about the rotor axis in a direction opposite to that of the rotor rotation.' Obviously, if practical flight is to be achieved this tendency must be balanced and- 7'0 controlled. This balance and control is obtained by the antitorque surfaces 46. These are placed inthe outer portion of the column of air.(or slip-stream) propelled .downwards by the fan action of the rotor and are so formed and each An opposite control motion produces the opposite rotation. Plainly, in addition to providing means for insuring a-correct torque balance, the hinged flaps and their control connections provide an effective means for directional control. while operating vertically with power on (as well as while operating under the auto-rotative condition).

Having risen from the take-olf spaceto a suf- 'flcient altitude to clear surrounding obstacles, the propulsion of the craft in any desired direction, and its control vertically and in forward ight, are effected generally as illustrated in the ,diagrams of Figures 9 and l0, and, for an alterand 34 may be disposed at the blade roots in/50 native form of construction, of Figure l5. In both forms of construction illustrated, propulsion is obtained by tilting the rotor forward, with relation to the horizontal. For the type of control illustrated in Figuresy 9 and l0 the center of gravity of the entire machine is placed, by a suitable disposition of the weights to be carried (dead weight and/or pay loads), at the point 84 which is slightly in front of the extension of the rotor axis 55. Since the thrust of the rotor always acts on the rotor hub I9 the machine may be considered as being freely suspended from its center. 'Ihen if the elevator 51 is tilted or deected to the position shown in Figure 9, so as to derive little or no force from the rotor slipstream, the center of gravity ofthe suspended structure will tend, under the influence of the gravity force indicated by the arrow 85, to take a position ver- 'tically under the hub, thus tilting the entire machine, including the rotor axis, forward. While the cone of the blade path will not tilt forward quite as much as thel rotor axis, nevertheless it also will tilt forward. Since the rotor thrust force indicated by the arrow 81 is always approximately in line with the cone axis, it will likewise tilt forward, thus becoming resolvable about the vertical axis and then proceeding in into the vertical lift force 88, which balances the gravity force 86, and the horizontal thrust force,

indicated by the short arrow I9, which propels the machine forward.

If, however, it is desired to remain stationary in the air, or to move only vertically through it, the elevator 51 is deflected, by a rearward motion of the handle of the (conventional) control stick, toward, or into, the position shown in Figure 10. The tabs Gli on the elevator are thus brought farther and more squarely into the downward air-flow or rotor slipstream and thus develop a downward force (indicated by the arrow) which tends to right the machine. Since this force acts on a much longer moment arm than the gravity force 86, it needs to be only comparatively small.

the desired direction. Invthe form of the construction shown in Figure 15, further means for lateral control may be provided by adding a pivot to allow lateral tilting of the rotor assembly in addition to the provision for longitudinal tilting If proportioned so as to produce an excess force,

in the position of Figure 10, the position there shown will develop a rearward tilt of the craft (and rotor axis) and cause the machine to move backwards, while an intermediate setting or position, (possibly between those indicated in Figures`9 and 10) will berequlred for complete ahsence of horizontal motion (hovering for instance). j

To obtain a high forward velocity the elevator is at first set in the position of Figure 9 which starts'the machine forward in response to the horizontal thrust component 88. As the forward motion'increases,the air flow over the elevator becomes inclined as the result of the combination of the horizontal relative wind and the rotor slipstream. The downward tail force is thus rst reduced still further and then, as the air iiow meets the under side of the elevator, the tail force is reversed. The upward force thus produced tilts the rotor still farther forward and thereby increasesl the magnitude of the horizontal force component. Thus, the forward motion and the upward tail force mutually increase each other until the maximum forward speed is attained, after which the elevator is used for longitudinal control, in a manner similar to the operation of conventional airplanes.

To reverse the process and bring the machine to a horizontal standstill, the `control stick is pulled well back, thus bringing the elevator 51 into a depressed setting which, by producing a down force on the tail, tilts the rotor axis rearward. 'Ihe resulting backward force component may bring the machiner to a stop within a very short distance.

With the modified or alternative form of control illustrated in Figure 15, the elevator is dispensed with and the rotor is tilted by moving the center of gravity of the suspended structure forward or backward, through the pendular shifting of the weight of the suspended fuselage and its contents. Thus, pulling back the control stick V'M from the position shown rotates the sprocket 1I, through the agency of the link 18 and the lever 13, thereby causing the ventire fuselage to move backward with relation to the rotor. The center of gravity, being thus moved out of` the vertical line through the suspension point in the rotor hub,l immediately swings back and so produces a backward inclination of the rotor axis and the rotor thrust force.' Similarly, the opposite motion of the control stick gives rise to forward propulsion and the control stick responsesA will in general be similar to those of the type of Figures 9 and 10.

The longiimdinal control means, together with the directional control means provide complete shown.

The power plantmay be either made to tilt along with the tilting of the rotor as is illustrated in Figure 15 or the power may be transmitted, through suitable universal joints, from the power plant, which is rigidly connected with the fuselage, to a tiltable rotor.

In tilting the power plant with the rotor,- the power plant may be reslliently anchored to the fuselage by being pivoted with respect thereto.

The rotor and its rigidly associated power plant may also be made to tilt in both a longitudinal direction and a transverse direction. In this case,

the engine would be pivotally anchored in the fore and aft or the longitudinal direction, and it might be spring-mounted or spring-confined in the transverse direction with the yield of the spring being suilicient to permit of the unnecessary lateralv deflection of engine and rotor.

By disposing the fuselage 6l and tail surface 11, (11 preferably xed, though it may be adjustable) with a normal forward and upward inclination (to a suitable degree) when the craft is in vertical operation (ascent, descent or hovering), the tail surface may automatically augment the tilting control. Thus, as forward speed is attained (by tilting about the pivot lll) the air stream passing the tail surface vil will act upwardly or on its lower surface and thus tilt the entire craft forwardly. This further increases the forward or horizontal component of the rotor thrust and thus further increases the forward speed. This progressive and cumulative forward tilting effect of the tail surface (11) ceases when it levels off into the line of forward travel, which should take place at full forward speed or at a substantial forward speed. By reason of this relationship between the manual tilting control (of tilting the rotor-motoranti-torque assembly relative to fuselage) and automatic and progressive tilting effect of the tail surface 1l, the angular displacement about the pivot l0 may be substantially reduced.

Since, in both embodiments of my invention (Figures 2 and 15) the antitorque surfaces are tilted forward with the rotor axis, it is evident (especially from Figure 14 which shows the attitude in full speed forward flight) that in all important forward ight conditions, a component of air flow exists across the antitorque surfaces and their control flaps. These aps `with their connections thus remain effective for directional control in forward flight with power on just as in vertical flight. Only in certain restricted conditions of ilight, such as a dive with low engine power,` does the air-flow become parallel to the anti-torque surfaces and the control aps therefore inoperative. A conventional rudder connected to the same' controls is optional for providing directional control in these cases One of the advantages of the novel arrangement of antitorque surfaces used in the craft of my present invention, is that not only does it provide the essential characteristic of symmetrical moment distribution, but it also presents only a small area in the direction of forward flight, and thus permits of relatively high speed lateral control when hovering, by first turning in forward night. In full speed forward flight equilibrium,

Anovel means of my .however, with the setting vof the anti-torque surfaces at a rightangle to the rotor axis, this advantage may not be fully realized because the angle of tilt, as illustrated by the solid lines in Figure 14, presents to the air-now (induced by night) in the direction of the arrow 9|, an unnecessarily large extent .of antitorque surface area, both for control purposes and from the standpoint of head resistance. To overcome this, the antitorque surfaces may be inclined relative to the rotor axis, in the vertical plane,

Ias indicated by the dotted lines in Figure 14,

craft, which otherwise would develop in the forward night, due to the support of the craft by a single articulated rotor. This novel phaseV or feature of my present invention is illustrated in Figures 11, 12 and 13. Figure 11 illustrates the side-displacement tendency referred to above. As viewed from the front, thel blades advance on the right side and retreat on the left side of the diagram, the relative velocity being therefore greater on the right than on the left. As a consequence, the lift force on the right is greater and the blades passing that side, in nnding an are raised to a higher position than they are when passing the left side. In other words, the cone axis is angularly displaced to the left. Since the rotor thrust, represented by the arrow 92, is in line with the cone axis, this force is also inclined to the left, giving rise to a lateral component force, indicated (qualitatively) by the short arrow 93 which produces objectionable side-slipping if not overcome. The

present invention for overcoming this, is illustrated in Figure 12. It con sists in inclining the antitorque surfaces 46 slightly with relation to the fuselage axis, so that they will be acted on, when in forward night in the direction of arrow 94, by the relative air now-to produce the side forces indicated by the arrows 95. By suitable proportioning and inclination, the sum of equal and opposite to the lateral force 93. 'I'he resulting balance is illustrated in Figure 13, in which the arrow 96 represents the sum of the compensating forces derived from the antitorque surfaces. It will be noted that the only unbalance remaining is that due to the force 96 acting at a lower point than force 99. This unbalance is in the nature of a simple rolling couple and may therefore be com` pletely balancedout by a slight dinerential set-y ting of the ailerons, resulting in the forces shown by the short arrows 91. While in the construction illustrated, the antitorque surfaces Y are employed to furnish the corrective-side-force,

this phase or feature of my invention is applicable also to rotative-winged aircraft without antitorque surfaces, by the use of auxiliary vanes suitably disposed, or with one auxiliary vane in front of the rotor axis to counterbalance a suitable lateral inclination of the conventional ver-' tical tail surfaces. of this phase 'of my invention, the fuselage itself may be employed to provide a lateral force by a suitable symmetrical construction or contour.

In still another embodiment A feature of the novel method for correcting the forward night unbalance disclosed above, is that it does not give rise to another lunbalance in slow forward and vertical night, as does the lateral offsetting of the rotor because all the forces involved, both'in producing the unbalance and in applying the corrective force, exist only in forward night and diminish proportionately as the horizontal speed is reduced.

In the case of power failure, either vaccidentally or by voluntary throttle control, the automatic pitch regulator instantly sets the rotor blades in the predetermined autorotative angular position; whereupon the air now caused by the motion of the machine through the air acts upon the blades to maintain the rotor in motion independent of the engine, as permitted bythe freewheel clutch unit. Descent at low speed may then be effected either nearly vertically or at along gliding angle in the manner already well known for purely autorotative aircraft.

In autorotative night, the control operations are somewhat altered, owing to the fact that the `torque reaction is no longer present, that the air now of the rotor-slipstream isv no longer available, and also that the airflow over the antitorque surfaces is upward instead of downward.

.The disappearance of the torque reaction requires that the antitorque surfaces musil be neutral with respect to the upward air flow, if turning or spinning generally about the rotor axis line is to be avoided. While antltorque surfaces may be provided which would be neutral in reversed airnow, their area would be undesirably large, and therefore, in the embodimentof my invention here disclosed, the neutralization is accomplished with the naps. Thus when passing from power-on night to autorotation, the pilot removes his feet from rudder bar 53 and, placing them on rudder bar 54, pushes forward ,with the right foot until the rudder bar 54 is brought into a generally transverse position. This action, by swinging the naps 41 to the dotted positions 56, causes the required neutralthese forces may be made the equal and opposite y ner.

ization of theantitorque surfaces with respect to the reversed air-now. 'Ihe rudder bar 54 is thereafter usedY for directional control. Since the cable connections of the rudder bar 54 are reversed (on account of the opposite location of the horn 52) the motions of the naps vare opposite to that produced by the rudder bar 53 (for similar 'motions of the feet). In the reversed airnow therefore, the control responses are the same. As rudder bar 54 is swung into the transverse position, the power-on rudder bar 53 swings out of the way.

With the rigid motor mounting, since the maintenance of the required attitude for vertical operation depends on the pressure derived from the slipstream, strictly (or theoretically) vertical descent in autorotation is not possible. With the pivoted rotor mounting however, the longitudinal control is entirely independent of the slipstream, and consequently absolutely vertical autorotation may be accomplished.

Stability and rolling control in forward night are provided by the use of dihedral surfaces and conventional ailerons in the well-known man- In vertical and low speed night, the cone angle of the rotor blades is adequate for stability. On the ground, there being'no propeller to provide horizontal thrust', the motor must be tilted to provide the propulsion needed for txying.

` With the nxed rotor mounting shown in Figures arcaica ble rotor assembly/shown in Figure 15, however,

the normal longitudinal control is effective onf the ground also.

One of the advantag of my novel construction over the purely autorotative, rotor supported aircraft, is that of control on the ground. Thus, the overturning tendency which has proved troublesome with this last-mentioned type craft, is avoided in my construction because the vertical force which is always available, when the engine is running, may be used to counteract any inclpient tendency to overturn.

While I have shown the various phases and features of my invention in certain specific embodiments or combinations, I am aware that my invention and the several phases or features thereof may be embodied in other forms without departing from the spirit or essential attributes thereof, and I therefore desire the present embodiments to be considered in all respects as lllustrative and not restrictive, reference being had to the appended claims rather than to the foregoing description, to indicate the scope of the invention.

Having thus described the invention what is hereby claimed as new and described to be secured by Letters Patent is:

1. In an aircraft, a lift screw, parallel antitorque surfaces disposed in two groups, one in front of and the other behind the rotational axis of said light screw, said surfaces each being parallel to the fore and aft axis of saldaircraft, and means for varying the effectiveness of said antitorque surfaces.

2. In an aircraft, a lift screw, a plurality of anti-torque surfaces arranged in two groups, one' group being mounted in frontof and the other group being mounted behind the rotational axis of said lift screw, the surfaces in each group being parallel to each other and all of said surfaces extending parallel to the fore and aft axis of said aircraft, generally horizontally hinged flaps attached to said anti-torque surfaces, and `control means for swinging said flaps about their hinges.

3. In an aircraft. a lift screw, antitorque surfaces, hinged ilaps attached to said anti-torque surfaces, a pivoted control lever operatively connected to said flaps, and a second pivoted control lever operatively connected to said flaps with reversed connections.

4. In an aircraft, an overhead power-driven lift screw mounted to rotate on an axis behind the center of gravity, an elevator surface at the rear, said elevator having forwardlyextending tabs movable into different angular settings relative to and within the slipstream of said overhead power-'driven lift screw, and means for controlling said elevator.

5.- In an aircraft, an overhead power-driven lift screw. and control means consisting in an` elevator having tabs' movable into different angular settings relative to and within the slipstreamof said overhead power-driven lift screw.

6. In an aircraft having a power plant, an aerodynamic lift unit mounted on said power plant in fixed axial relation thereto and antitorque surfaces rigidly connected to said power plant for opposing the torque reaction set up by said aerodynamic lift unit, a fuselage pivotaliy attached to said power plant, and means for tilting said fuselage relative to said power plant and said rigidly connected lanti-torque surfaces.

9 'hlnanaircrafthavingapowerplantalift screw mounted on said power plant in fixed axial relation thereto and anti-torque surfaces rigidly connected to said power plant for opposing the torque reaction set up by said lift screw, a fuselage pivotally attached to said power plant, and means for tilting saidfuselage relative to slid power plant and said rigidly connected antltorque surfaces.

8. In an aircraft, a power plant, a lift screw mounted on said power plant in fixed allal relation thereto, anti-torque surfaces rigidly attached to said power plant, a fuselage pivotnlly attached to said power plant, and means for lting said fuselage relative to said power plant. 9. An aircraft supported by rotating articulated -airfoils capable of producing a side force at the hub of said aurons during forward night, and a non-rotating structure extending ahead of and behind the axis of rotation of said airfoils and capable of producing aerodynamic side forces in forward flight all acting in a direction opposite that of the side force at said huh, thereby to avoid yawing during forward flight.

10. In an aircraft, a lift screw, a liquid cooled engine adapted to drive said lift screw, antitorque surfaces, radiating means forming part of said surfaces and means for circulating liquid from the engine through said radiating means.

11. In an aircraft, a lift screw, a liquid cooled engine adapted to drive said lift screw, antitorque surfaces supported by tubular members. radiating means within said surfaces and snitable connections for the circulation of the cooling liquid through said tubular members.

12. In an aircraft having an overhead powerdriven lift screw as its sole means of propulsion, means for supporting said aircraft on the grmmd comprising a plurality of ground contacting members, and m'eans for varying the elective height of at least one of said members whereby the lift screw axis may be tilted relative to the ground to provide a propulsive force for tauing.

13. In an aircraft having an overhead powerdriven lift screw as its sole means of propulsion, `means for adjusting the undercarrlage whereby thelift screw axis may be tilted relative to the ground to provide a propulsive force for taxying.

14. An aircraft having a power plant, a lift screw, driving means intermediate said lift screw and power plant, means for automatically varying the pitch of the lift screw, and generally parallel anti-torque surfaces disposed ahead of and behind the center of gravity of said aircraft for neutralizing the torque reaction of the lift screw, said surfaces each being generally parallel to the normal forward vflight direction.

t 15. An aircraft having a power plant, a liftY screw, driving means intermediate said lift screw and power plant, means for automatically disengaging the power drive, means for automatically varylng the pitch of Vthe lift screw, generally parallel anti-torque surfaces disposed ahead of and behind the center of gravity of said aircraft for neutrallmng the torque reaction of the lift screw, said surfaces each being generally parallel to the normal forward flight direction and means for varying the effectiveness `of said antltorque surfaces.

16. An aircraft having a power plant, a lift screw, driving means intermediate said lift screw and power plant, means for automatically disengaging the power drive, means for automatically varying the pitch of the lift screw, generally parallel anti-torque surfaces disposed ahead of and behind the center of gravity of said aircraft for neutralizing the torque reaction of the lift screw, said surfaces each being generally parallel to the normal forward night direction means for varying the effectiveness of said anti-torque surfaces, and means separate from said antitorque surfaces coacting with the slipstream of the lift screw for tilting the lift screw relative to the horizontal.

17. An aircraft having a fuselage, a power plant, a lift screw, driving means intermediate said lift screw and power plant, means for automatically disengaging the power drive, means for automatically varying the pitch of the lift screw, generally parallel anti-torque surfaces disposed ahead of andbehind the center of gravity of said aircraft for neutralizing the torque reaction of the lift screw, said surfaces each being rigidly attached to said power plant generally parallel to the normal forward night direction,

and anti-torque control means concentrically related at oneportion thereof with the pivot between power plant and fuselagefor varying the effectiveness of said anti-torque surfaces. r

19. In an aircraft, hovering means 'comprising an overhead power-driven lift screw-,a powerv plant for rotating said lift screw, and control means consisting of an adjustable elevator pivotable about an axis generally transverse to the longitudinal axis of the craft and formed with tabs movable into different angular settings relal tive to and within the slipstream of said powerdriven lift screw, whereby the direction of the axis of rotation of said liftscrew may be varied to control horizontal movement of the aircraft.

20. In an aircraft, hovering means comprising a lift screw, a power plant for rotating said lift screw, variable anti-torque surfaces constituting directional control means, and means for controlling the direction of the axis of rotation of said lift screw comprising a fuselage pivotally and directly attached to said power plant and means for tilting said fuselage relative to said power plant, whereby horizontal movement of said aircraft may be controlled.

2l. In an aircraft including `an overhead power-driven lift screw rotating about an axis behind the center of gravity of said aircraft and a power plant for rotating said lift screw, means for tilting the axis of rotation of said powerdriven lift screw consisting in a transversely pivoted controllable vane at the rear of the aircraft continuously surfaced on its opposite sides, said vane being adapted to coact with both the slipstream of said overhead power-driven lift screw and the relative horizontal air-now on opposite surfaces thereof, whereby longitudinally movement of the aircraft may be effected.

22. In an aircraft including a lift screw mounted on a power plant in fixed axial relation thereto and a fuselage pivotally attached to -said power plant, limited means for assisting longitudinal movement of the` aircraft comprising an upwardly tilted tail surface rigidly secured to said fuselage and adapted to aid longitudinal movement by coacting with the relative horizontal air-now on the under side thereof.

23. In an aircraft including a lift screw rotating aboutan axis behind the center of gravity, longitudinal and directional control means, said longitudinal control means consisting of a controllable vane at the rear coacting with the slipstream of the lift screw, and said directional control means including generally vertically disposed and generally parallel surfaces mounted ahead of and behind the center of gravity, .generally horizontal hinged flaps attached to said surfaces and means for swinging said naps about their hinges.

24. In an aircraft including a power plant, a lift screw mounted on said power plant in fixed axial relation thereto and a fuselage pivotally attached to said power plant, longitudinal and directional control means, and longitudinal control means consisting of means for tilting said fuselage relative to said power plant, and said directional control means including generally vertically disposed and generally parallel surfaces mounted ahead of and behind the center of gravity, generally horizontally hinged flaps attached to said surfaces and means for swinging said flaps about their hinges.

25. In an aircraft supported by a power-driven articulated rotor, automatic means for producing a corrective side force directly proportional to the longitudinal air-velocity of the aircraft, said means comprising aerodynamically active surfaces disposed ahead of and behind the axis of rotation of said rotor, said surfaces being inclined with respect to the line of night.

26. In an aircraft having a lift screw and antitorque surfaces generally parallel to the line of night, means for setting the leading edges of said anti-torque surfaces at an angle to a plane normal to the axis of rotation of said lift screw,

whereby the relative effectiveness of said antitorque surfaces may be adjusted for forward flight. i

27. In an aircraft supported by rotating airfoils and having generally vertical control surfaces,

means for setting the upper edges of said control surfaces at an angle to a plane normal to the axis of rotation of said supporting airfoils, whereby the relative effectiveness of said control surfaces may be adjusted for forward night.

28. In an aircraft supported by rotating airfoils and having generally vertical control sur,- faces, means for reducing the wind resistance of said control surfaces in forward night, said means including means for setting the upper edges of said surfaces at an angle to a planenormal to the axis of rotation of the supporting airfoils.

29. In an aircraft of the class described and including a single articulated rotor capable of producing a side force at the rotor hub during forward night and aerodynamically active surfaces inclined tothe normal line of night capable of producing corrective side forces, but spaced from saidl hub, the combination of said rotor and said aerodynamically active surfaces being capable of producing in vforward night a rolling couple, means for neutralizing said rolling couple and thereby providing stability in forward night comprising a pair of pivoted ailerons disposed at the tail of said craft. I

30. An aircraft of the class described including a fuselage, a plurality of frame members rigidly connected to said fuselage and extending upwardly therefrom, a power plant pivotally supported between said upwardly extending frame members in spaced relation from saidfuselage, said power plant being pivotable about an axis generally transverse to the normal forward'flight direction, a single lift screw mounted immediately above said power plant in coaxial relation thereto, adjustable means interconnecting said power plant with said fuselage for longitudinally tilting said lift screw about said transverse axis, and anti-torque airfoil surfaces rigidly connected to said power plant fore and aft and disposed with- -vin the slip stream of said lift screw and provided with controllable hinged aps affording directional control means.

31. In an aircraft, a lift-screw, parallel anti' torque airfoil surfaces supported on the aircraft by means leaving substantially unobstructed the leading edge of the anti-torque surfaces, said anti-torque surfaces cooperating with the slip stream of the lift-screw to oppose the torque reaction thereof,said anti-torque surfaces being disposed in two groups, fore and aft, respectively,

of the line of the axis ofv rotation of the liftscrew, said groups of'anti-torque surfaces producing more ori less approximately equal antitorque moments, and the surfaces of each group being generally parallel to each other and all the anti-torque surfaces being generally parallel to the fore and aft axis of the aircraft.

32. In an aircraft, a lift-screw, parallel antitorque airfoil surfaces supported on the aircraft by means leaving substantially unobstructed the leading edge of the anti-torque surfaces, said anti-torque surfaces cooperating with the slipstream of the lift-screw to oppose the torque reaction thereof, `said anti-torque surfaces being disposed fore and aft, respectively, of the line of the axis of rotation of the lift-screw, said anti-torque surfaces producing more or less approximately equal anti-torque moments, and said anti-torque surfaces being generally parallel to each other and to the fore and aft axis of the aircraft.

HAVILAND H. PLATT. 

